Revert "Add Gray8 pixel config"

This reverts commit f2956459f707de596dcb2c79a7ee1fa62d599c0d.

Reason for revert: GM and image failures on some bots (rendering red, not gray).

Original change's description:
> Add Gray8 pixel config
> 
> This is still just linear (non-sRGB), but adding sRGB will
> be the next step. I've verified that this is really making
> R8 textures when uploading Gray8 bitmaps. Tests pass, and
> the all_bitmap_configs GM still renders correctly (unlike
> when we just mapped Gray8 to Alpha8).
> 
> This adds another pixel config, which could grow our cache
> footprint, but the benefits of not using 4bpp for 1bpp data
> should outweigh that?
> 
> BUG=skia:6110
> 
> Change-Id: I4fc4c2479fc25f1d278e174a9bb5b542a0cb184c
> Reviewed-on: https://skia-review.googlesource.com/6817
> Reviewed-by: Brian Salomon <bsalomon@google.com>
> Commit-Queue: Brian Osman <brianosman@google.com>
> 

TBR=bsalomon@google.com,robertphillips@google.com,brianosman@google.com,reviews@skia.org
BUG=skia:6110
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Change-Id: I95a4fc0450a569d5791f6bceb7fae61c7e5eba61
Reviewed-on: https://skia-review.googlesource.com/6838
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
11 files changed